void insertion_sort(int arr[], int len) {
  int i, j, temp;
  for (i = 1; i < len; i++) {
    temp = arr[i];
    for (j = i; j > 0 && arr[j - 1] > temp; j--)
      arr[j] = arr[j - 1];
    arr[j] = temp;
  }
}